Reproduction 367 



plant. Again, if the young ears of sweet corn are pol- 

 linated with a pollen from Dent and Flint varieties, there 

 result many seeds with smooth kernels and starchy endo- 

 sperm (Fig. 104). These results may be secured with pure- 

 line strains under control conditions, and the phenomenon 

 is recognized as xenia. Characters such as those above 

 noted alone exhibit true xenia; thus color or chemical 

 content, qualities which reside in the endosperm, are of 

 this nature, while qualities evident through the embryo 

 belong to another category. The explanation of this en- 

 dosperm phenomenon has now been found in the process 

 . of double-fertilization. 



Generally the nucleus and cytoplasm of the embryo-sac 

 develop the endosperm, and only the pistil-bearing plant 

 is concerned with the qualities of this material. In the 

 lily, in corn, and in many other cases more recently made 

 known, the nucleus of the embryo-sac may fuse with the 

 second sperm nucleus from the pollen-tube, and thus the 

 endosperm may acquire, as well as the embryo, qualities 

 of the pollen-producing plant. It is evident that corn 

 which possesses color by virtue of a pigment in the pericarp 

 will not show this type of phenomenon, for the pericarp has 

 no means of becoming immediately endowed with the 

 qualities brought by the pollen. Cases of xenia, therefore, 

 should not be confused with ordinary speckled ears. The 

 latter may result in the second generation, or later, from 

 crosses in which color is one of the characters of one or 

 both parents, or from bud variation. Xenia is a question 

 of physiological interest in plant production, but it has 

 apparently very little practical bearing. When it exists, 

 it is an infallible sign of hybridization, and in some cases 



